diff --git a/docs/src/cluster/synchronization.md b/docs/src/cluster/synchronization.md
index 1e80a0e91..5a0829b99 100644
--- a/docs/src/cluster/synchronization.md
+++ b/docs/src/cluster/synchronization.md
@@ -8,7 +8,7 @@ Solana takes a very different approach, which it calls _Proof of History_ or _Po
 
 Solana technically never sends a _block_, but uses the term to describe the sequence of entries that validators vote on to achieve _confirmation_. In that way, Solana's confirmation times can be compared apples to apples to block-based systems. The current implementation sets block time to 800ms.
 
-What's happening under the hood is that entries are streamed to validators as quickly as a leader node can batch a set of valid transactions into an entry. Validators process those entries long before it is time to vote on their validity. By processing the transactions optimistically, there is effectively no delay between the time the last entry is received and the time when the node can vote. In the event consensus is **not** achieved, a node simply rolls back its state. This optimisic processing technique was introduced in 1981 and called [Optimistic Concurrency Control](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.65.4735). It can be applied to blockchain architecture where a cluster votes on a hash that represents the full ledger up to some _block height_. In Solana, it is implemented trivially using the last entry's PoH hash.
+What's happening under the hood is that entries are streamed to validators as quickly as a leader node can batch a set of valid transactions into an entry. Validators process those entries long before it is time to vote on their validity. By processing the transactions optimistically, there is effectively no delay between the time the last entry is received and the time when the node can vote. In the event consensus is **not** achieved, a node simply rolls back its state. This optimisic processing technique was introduced in 1981 and called [Optimistic Concurrency Control](https://en.wikipedia.org/wiki/Optimistic_concurrency_control). It can be applied to blockchain architecture where a cluster votes on a hash that represents the full ledger up to some _block height_. In Solana, it is implemented trivially using the last entry's PoH hash.
 
 ## Relationship to VDFs